OG QR 2nd Ed. DS #63

This topic has expert replies
Junior | Next Rank: 30 Posts
Posts: 13
Joined: Thu Apr 19, 2012 2:23 pm

OG QR 2nd Ed. DS #63

by tofubeans » Fri Apr 27, 2012 11:37 am
63) A Town T has 20,000 residents, 60 percent of whom are female. What percent of the residents were born in Town T?

1) The number of female residents who were born in Town T is twice the number of male residents who were not born in Town T.

2) The number of female residents who were not born in Town T is twice the number of female residents who were born in Town T.
Source: — Data Sufficiency |

User avatar
Community Manager
Posts: 1060
Joined: Fri May 13, 2011 6:46 am
Location: Utrecht, The Netherlands
Thanked: 318 times
Followed by:52 members

by neelgandham » Fri Apr 27, 2012 2:58 pm
Total number of residents = 20000
Total number of female residents = 12000
Total number of male residents = 8000

Let the number of females born in town T = x
Then the number of females not born in T = 12000-x
Let the number of males born in town T = y
Then the number of males not born in T = 8000-y
The question can now be rephrased to 'What is the value of ((x+y)/20000)*100 ?
(1) The number of female residents who were born in Town T is twice the number of male residents who were not born in Town T.
x=2*y. So, ((x+y)/20000)*100 = (3y)/200. Since we don't know the value of y, statement I is not sufficient to answer the question
(2) The number of female residents who were not born n Town T is twice the number of female residents who were born in Town T.
12000-x = 2x
3x = 12000
x = 4000
So, ((x+y)/20000)*100 = (4000+y)/200. Since we don't know the value of y, statement II is not sufficient to answer the question
From I and II
x = 2y = 4000, implies y = 2000.So, ((x+y)/20000)*100 = (4000+2000)/200 = 30%. So, Statement I + Statement II combined works great. IMO C
Anil Gandham
Welcome to BEATtheGMAT | Photography | Getting Started | BTG Community rules | MBA Watch
Check out GMAT Prep Now's online course at https://www.gmatprepnow.com/

Junior | Next Rank: 30 Posts
Posts: 17
Joined: Sun Apr 22, 2012 11:22 am

by jrakhe » Fri Apr 27, 2012 4:07 pm
I think each statement is enough.

Senior | Next Rank: 100 Posts
Posts: 59
Joined: Sun Mar 11, 2012 8:57 pm
Location: India
Thanked: 16 times
Followed by:1 members

by shantanu86 » Fri Apr 27, 2012 5:40 pm
jrakhe wrote:I think each statement is enough.
Hi jrakhe,

Total population of T = 20,000
Total males = 8,000.
Total females = 12,000

Let number of males born in town T = M
Let number of females born in town T = F

Now, for two variables we will need two *distinct* equations.

Lets examine..

1) The number of female residents who were born in Town T is twice the number of male residents who were not born in Town T.

=> F = 2*(8000 -M)

2) The number of female residents who were not born in Town T is twice the number of female residents who were born in Town T.

=> (12000 -F) = 2*F

Thus, since 1.) and 2.) are distinct they will give unique value of M and F, from which the required % will be (M+f)/20000*100

Hope it helps!!
If you feel like it, hit thanks :)

User avatar
Newbie | Next Rank: 10 Posts
Posts: 8
Joined: Sun Jan 01, 2012 2:55 am
Thanked: 1 times

by fyllmax » Sat Apr 28, 2012 3:54 am
IMO:C

User avatar
GMAT Instructor
Posts: 1462
Joined: Thu Apr 09, 2015 9:34 am
Location: New York, NY
Thanked: 39 times
Followed by:22 members

by Jeff@TargetTestPrep » Mon Dec 18, 2017 9:10 am
tofubeans wrote:63) A Town T has 20,000 residents, 60 percent of whom are female. What percent of the residents were born in Town T?

1) The number of female residents who were born in Town T is twice the number of male residents who were not born in Town T.

2) The number of female residents who were not born in Town T is twice the number of female residents who were born in Town T.
We are given that of the 20,000 residents in Town T, 20,000 x 0.6 = 12,000 are female, and thus 8,000 are male. We need to determine the percentage of residents who were born in Town T.

Statement One Alone:

The number of female residents who were born in Town T is twice the number of male residents who were not born in Town T.

We can let the number of male residents born in Town T = m, and the number of female residents born in Town T = f. Thus, (8,000 - m) males and (12,000 - f) females were not born in Town T.

From the statement, we see that f = 2(8,000 - m). However, we still cannot determine the percentage of residents who were born in Town T. Statement one alone is not sufficient to answer the question.

Statement Two Alone:

The number of female residents who were not born in Town T is twice the number of female residents who were born in Town T.

We can let the number of female residents born in town T = f. Thus, (12,000 - f) females were not born in Town T.

From the statement, we see that (12,000 - f) = 2f. Solving for f, we have:

3f = 12,000

f = 4,000

However, we still cannot determine the percentage of residents who were born in Town T, since we don't know the number of males who were born in Town T. Statement two alone is not sufficient to answer the question.

Statements One and Two Together:

Using both statements, we see that f = 2(8,000 - m) and f = 4,000. Thus:

4,000 = 2(8,000 - m)

4,000 = 16,000 - 2m

2m = 12,000

m = 6,000

So, 4,000 females and 6,000 males were born in Town T, which is 10,000 people.

Thus, 10,000/20,000 = 50% of the residents were born in Town T.

Answer: C

Jeffrey Miller
Head of GMAT Instruction
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews